Microcalorimetric Measurement Of The Enthalpies Of Transfer Of A Series Of M-alkoxyphenols From Isotonic Aqueous Solution To Escherichia Coli Cells

Enthalpies of interactions of a series of m-alkoxyphenols with non-growing Escherichia coli suspended in a salt solution have been recorded. These data have been analysed on the assumption that the initial relatively rapid endothermic process represented the transfer of solute from aqueous solution to cells (ΔHtrs) and that the subsequent relatively lengthy exothermic process resulted from the biological consequences of the transfer process itself. The derived values are compared with values of ΔHtrs found for transfer of these solutes from water to octan-1-ol, heptane and propylene carbonate.8292929293

Self-organization of stack-up block copolymers into polymeric supramolecules

Polyethylene oxide –b– polypropylene oxide -b- polyethylene oxide (EO106PO70EO106) block copolymer self-organizes into polymeric supramolecules, characterized by NMR as phase transition from the isotropic stack-up block structure to the ordered cubic polymeric supramolecular structure. Its dependence on both temperature and copolymer concentration is clearly shown by the changes in line shape and chemical shift of the PO70blockβ,γresonances

Determination Of Thermodynamic And Kinetic Parameters From Isothermal Heat Conduction Microcalorimetry: Applications To Long-term-reaction Studies

The application of heat conduction isothermal microcalorimetry has been proposed for some time as a rapid and general technique for the determination of both thermodynamic and kinetic parameters of chemical reactions. These applications have been suggested as being of particular relevance to solid-state reactions and, industrially important, to the prediction of long-term stability and of compatibility data for pharmaceutical materials. However, there has yet to be the development of a general procedure that does not require additional noncalorimetric data and that is free of assumptions, which can be used to determine the thermodynamic and kinetic parameters for a reaction, from calorimetric data. It is the purpose of this paper to describe such a general approach which does not depend upon knowledge of initial concentrations (quantity), enthalpy, or any predetermined reaction order. Equations have been developed which incorporate calorimetrically accessible data (Φ, the power, and q, the heat output) and which also include the rate constant, k, the change in enthalpy of the reaction, ΔH, and the order of reaction. A second procedure is also described which depends only on the analysis of the calorimetric signal and which involves no formal chemical kinetic based equations. The methods described allow estimation of, for example, the annual extent of degradation of a solid compound. The methods developed have been tested through examination of both calculated and experimental data. The experimental work examined very slow reactions (lifetime of years) of known order (there are little reliable enthalpy data available for slow reactions) and involved calorimetric observation of these reactions for up to 50 h. In all cases, the method yielded the appropriate, i.e., conforms to literature data, rate constant, reaction order, and, where available, reaction enthalpy. Some situations in which this microcalorimetric approach and subsequent data analysis will be of utility are discussed. © 1995 American Chemical Society.99187108711

Determination of Michaelis-Menten parameters obtained from isothermal flow calorimetric data

Recent papers have reported [Thermochim. Acta 399 (2003) 63; Thermochim. Acta, in press] the results of a preliminary inter/intra laboratory study into the suitability of the base-catalysed hydrolysis of methyl paraben as a test and reference reaction for isothermal flow-through calorimeters. It was shown that this reaction can be used to investigate the flow characteristics of the instrument being used. It has also allowed, for the first time, the calculation of accurate values for the rate constant and for the enthalpy change, DeltaH (hereafter H (enthalpy) for simplicity) of reaction directly from the calorimetric data, free from assumption. These findings have been extended to permit the direct determination of Michaelis-Menten based kinetic parameters from calorimetric data again free from assumption (except that the system conforms to Michaelis-Menten kinetic theory). This paper describes the method used for such an analysis and reports the results of a preliminary study on the urea/urease enzymatic system

Determination Of Log P(app) For Drug Transfer To Microbial Cellular Systems Via The Taylor-aris Modified Diffusion Technique

Partitioning is a key process in QSAR studies. Experimental and calculated log P can be obtained. In the search for new methods of obtaining partition coefficients we have modified the Taylor-Aris diffusion technique to allow the direct measurement of log P within the cell system itself. This technique is applied successfully to two different cell systems and an extrathermodynamic equation between log P for Escherichia coli and Saccharomyces cerevisiae seems to be a promising way of obtaining this parameter directly from them.172102108Leo, A., Hansch, C., Elkins, D., (1971) Chem. Rev., 71, pp. 525-616Takacsnovak, K., Avdeef, A., (1996) J. Pharm. Biom. Anal., 14, pp. 1405-1413Gluck, S.J., Benko, M.H., Hallberg, R.K., Steele, K.P., (1996) J. Chromatogr. A, 744, pp. 141-146Finizio, A., Vighi, M., Sandroni, D., (1997) Chemosphere, 34, pp. 131-161Rekker, R.F., (1977) The Hydrophobic Fragmental Constant, , Elsevier, AmsterdamHenczi, M., Nagy, J., Weaver, D.F., (1994) J. Liq. Chromatogr., 77, pp. 2605-2613Nowotinik, D.P., Feld, T., Nunn, A.D., (1993) J. Chromatogr., 630, pp. 105-115Montanari, M.L.C., Montanari, C.A., Pilo-Veloso, D., Cass, Q.B., (1997) J. Liq. Chromatogr. & Relat. Technol., 20, pp. 1703-1715Foster, M.D., Synovec, R.E., (1996) Anal. Chem., 68, pp. 2838-2844Braumann, T., (1986) J. Chromatogr., 373, pp. 191-225Kaliszan, R., (1990) Quant. Struct.-Act. Relat., 9, pp. 83-87Kaliszan, R., Kaliszan, A., Wainer, I.W., (1993) J. Pharm. Biom. Anal., 11, pp. 505-511Hsieh, M.-M., Dorsey, J.G., (1993) J. Chromatogr., 631, pp. 63-78Kumarik, K., Sukumaran, K., Taylor, S., Chang, C.A., Nunn, A.D., Tweedle, M.F., (1994) J. Liq. Chromatogr., 17, pp. 3735-3746Ajufo, M.A., Burke, A., Perkins, M.J., Beezer, A.E., Mitchell, J.C., Volpe, P.L.O., (1991) J. Chem. Soc., Faraday Trans., 87, pp. 2741-2744Loh, W., Tonegutti, C.A., Volpe, P.L.O., (1993) J. Chem. Soc., Faraday Trans., 89, pp. 113-118Pratt, K.C., Wakeham, W.A., (1975) Proc. Roy. Soc. Lond. A, 342, pp. 401-419Wakeham, W.A., (1981) Faraday Symp. Chem. Soc., 15, p. 145Alizadeh, A., Nieto De Castro, C.A., Wakeham, W.A., (1980) Int. J. Thermophysics, 1, pp. 243-284Ouano, A.C., Carothers, J.A., (1975) J. Phys. Chem., 79, pp. 1314-1318Walters, R.R., Graham, J.F., Moore, R.M., Anderson, D.J., (1984) Anal. Biochem., 140, pp. 190-195Loh, W., Beezer, A.E., Mitchell, J.C., (1994) Langmuir, 10, pp. 3431-3434Mall, S., Buckton, G., Gregori, T., Rawlins, D.A., (1995) J. Phys. Chem., 99, pp. 8356-8361Bello, M.S., Rezzonico, R., Righetti, P.G., (1994) Science, 266, pp. 773-776Beezer, A.E., Mitchell, J.C., Andrews, D.J., (1992) Pest. Sci., 35, pp. 375-379Taylor, G.I., (1953) Proc, Roy. Soc. A, 219, pp. 186-203Taylor, G.I., Proc. Roy. Soc. A, 223, pp. 446-468Taylor, G.I., (1954) Proc. Roy. Soc. A, 225, pp. 473-477Aris, R., (1957) Chem. Eng. Sci., 6, pp. 262-268Burkey, T.J., Griller, D., Lindsay, D.A., Sciano, J.C., (1984) J. Am. Chem. Soc., 106, pp. 1983-1985Tominaga, T., Yamamoto, S., Tanaka, J., (1984) J. Chem. Soc., Faraday Trans. 1, 80, pp. 941-947Price, W.E., (1989) J. Chem. Soc., Faraday Trans, 1, 85, pp. 415-419Ashby, L., (1991), PhD Thesis, University of LondonMontanari, M.L.C., (1991), M.Sc. Thesis, University of LondonMontanari, M.L.C., (1998), PhD Thesis, University of Minas GeraisCraig, P.N., (1971) J. Med. Chem., 14, pp. 680-684Craig, P.N., (1990) Comprehensive Medicinal Chemistry - The Rational Design, Mechanistic Study & Therapeutic Applications of Chemical Compounds, 4, pp. 645-666. , Hansch, C. (Ed.), Pergamon PressVan De Waterbeemd, H., (1983) Quantitative Approaches to Drug Design, pp. 183-192. , Dearden, J.C. (Ed.)Kaliszan, R., (1993) J. Chromatogr., 656, pp. 417-435Fujita, T., (1990) Comprehensive Medicinal Chemistry - The Rational Design, Mechanistic Study & Therapeutic Applications of Chemical Compounds, 4, pp. 497-560. , Hansch, C. (Ed.), Pergamon PressFujita, T., (1997) Quant. Struct.-Act. Relat., 16, pp. 107-112Hansch, C., Muir, R.M., Fujita, T., Maloney, P.P., Geiger, F., Streich, M., (1963) J. Am. Chem. Soc., 85, pp. 2817-10000Hansch, C., Fujita, T., (1964) J. Am. Chem. Soc., 86, pp. 1616-1626Tute, M.S., Lipophilicity in Drug Action and Toxicology (1996) Methods and Principles in Medicinal Chemistry, 4, pp. 7-26. , Pliska, V., Testa, B. and van de Waterbeemd, H. (Eds.), VCH, Weinheim Mannhold, R., Kubinyi, H. and Timmerman, H. (Eds.)Kubinyi, H., QSAR: Hansch Analysis and Related Approaches (1993) Methods and Principles in Medicinal Chemistry, 1. , VCH, Weinheim Mannhold, R., Krogsgaard-Larsen, P. and Timmerman, H. (Eds.)Hansch, C., (1993) Acc. Chem. Res., 26, pp. 147-153Collander, R., (1951) Acta Chem. Scand., 5, pp. 774-78

Dendrimers as potential drug carriers; encapsulation of acidic hydrophobes within water soluble PAMAM derivatives

This paper describes the synthesis of three neutral water soluble poly(amidoamine) (PAMAM) dendrimer derivatives. The ability of the two larger dendrimers to bind small acidic hydrophobic molecules is reported. Spectroscopic data and pH behaviour suggested that the acidic hydrophobes were forming stable ion pairs with the dendrimer's internal, basic tertiary nitrogens. With respect to forming 1:1 and 2:1 substrate/dendrimer complexes, both of the larger dendrimers were equally efficient at binding. All dendrimer/substrate complexes were completely miscible with water in all proportions (i.e. infinitely water soluble). When the bound substrates are drug moieties, then the resulting complexes could be considered as potential drug delivery systems. Flow calorimetry demonstrated that the dendrimers were able to release their hydrophobic guests when in contact with a biological cell

Thermodynamic considerations of microgel swelling behavior

A simple but novel thermodynamic model is presented, based upon van't Hoff analysis, for the reversible swelling behavior of colloidal microgels. The swelling, as a function of temperature, of poly(N-isopropylacrylamide/N,N'-methylenebisacrylamide) as well as poly(N-isopropylacrylamide/vinylpyridine/N,N'-methylenebisacrylamide) and poly(N-isopropylacrylamide/acrylic acid/N,N'-methylenebisacrylamide) microgel dispersions in H2O and D2O has been studied by photon correlation spectroscopy (PCS). PCS data was used to obtain the hydrodynamic diameter and hence the volume of the microgels (before and after reconstitution following freeze-drying) as a function of temperature. The choice of standard reference states, for analyzing the data attained, is discussed, and the one selected is that of the volume of the microgels at 333 K in H2O. For all microgels examined the volume, at this temperature, is shown to be independent of solvent (H2O, D2O). The derived data has allowed the exploration of a novel thermodynamic approach to the study of the swelling behavior of the microgels. The constant volume, at 333 K, for each of the polymer systems constituting the microgels is suggested to be an intrinsic property of the polymers themselves

Thermodynamic analysis of scanning calorimetric transitions observed for dilute aqueous solutions of ABA block copolymers

Dilute aqueous solutions of a series of poly(oxyethylene)-poly(oxypropylene)-poly(oxyethylene) block polymers have been shown to undergo phase transitions. A high-sensitivity differential scanning calorimetric (HSDSC) study of these block copolymers bas enabled the thermodynamic parameters for the phase transitions to be obtained. The thermodynamic parameters are all dependent on poly(oxypropylene) content of the polymer and riot on poly(oxyethylene) content or total polymer molecular mass. The importance of the poly(oxypropylene) in determining the aqueous solution phase properties of these polymers is further emphasized by the positive value for the heat capacity change from pre- to postphase transition. A positive heat capacity change is characteristic of "melting" of water ordered by exposed nonpolar groups. The work reported in this paper shows that the thermodynamic parameters describing the polymer phase transitions can be derived from basic thermodynamic principles and from consideration of the poly(oxypropylene) content. The theoretical analysis described in this paper also predicts that these polymers should undergo a second phase transition at high temperature and indeed these transitions have been detected by HSDSC